What's eating holes in my lily pads?

[havefun]

I know there are a lot of possible culprits but this has me stumped. Whatever it is it doesn't actually "eat" the hole, but rather, just "cuts" the hole. I find the middle pieces floating in the water. I'm almost positive it's not aphids because I don't see any. I know there is another bug that cuts a hole then lays its eggs on the underside of the leaf but I don't see any eggs. I've checked the underside of the leaves for weeks now but don't see anything crawling/chewing on them. I've gone out at night with a flashlight but didn't see anything. I've started putting mosquito dunks in, in the hopes that it will kill whatever this bug is.

Any ideas?

Thanks!